Edit (Fix): Use nearby identifiers as additional context

[umpox]

What:

• We think we can improve the performance of “Ask Cody to Fix” by including nearby identifiers as additional context.

How:

• Use bfg/contextForIdentifiers, provide identifiers from the range of the fix.
• Also consider extracting identifiers from the diagnostic. For example, many diagnostics include a Markdown message with more information. It is possible that we could extract these, search for them in the document and them provide them to bfg/contextForIdentifiers.